There has been known the COC (Chip on Chip) technique for laminating a plurality of semiconductor devices such as a memory and a logic in a three-dimensional fashion to achieve high performance, multiple functions, and miniaturization of electronic equipment such as mobile equipment. Among such semiconductor apparatuses utilizing the COC technique, a semiconductor apparatus having two pieces of semiconductor devices, which are micro-bump connected to each other, is advantageous to the miniaturization and an increase in data transfer speed between chips, and therefore, has been frequently used in various kinds of electronic equipment.
Such a semiconductor apparatus having the COC structure utilizing the micro-bump connection has been conventionally fabricated by joining respective terminals of surfaces (circuit forming surfaces) of the two pieces of semiconductor devices via a solder bump, followed by filling a clearance defined between the upper and lower semiconductor devices with an under-fill material (i.e., an UF resin). The solder bump is formed on a terminal of at least either one of the semiconductor devices to be joined to each other, and then, is melted by reflowing, and thus, the semiconductor devices are joined to each other.
A lead-free solder (such as Sn—Cu or Sn—Ag) is generally used as the solder bump from the viewpoint of conservation of the environment. An annular dam is formed on the lower semiconductor device so as to prevent the resin from flowing in an electrode pad outside of a specified region when the clearance is filled with the under-fill material.
However, in the case where the dam is formed of the solder, metal of a solder material is plated on the semiconductor device, to be then melted by reflowing. During this reflowing, the solder is coagulated at mainly the corner of the dam, and therefore, a solder sump is generated, thereby inducing a crack on a wafer or deficient bump connection.
In view of the above, a technique capable of suppressing the generation of a solder sump on a semiconductor device has been demanded.